String Methods

Method	Description
`upper()` / `lower()`	Change case
`strip()` / `lstrip()` / `rstrip()`	Trim whitespace
`replace(old, new)`	Replace substring
`split(sep)`	Split into a list
`join(iterable)`	Join strings with separator
`find(sub)` / `index(sub)`	Locate substring
`startswith(prefix)` / `endswith(suffix)`	Prefix / suffix check
`isdigit()` / `isalpha()` / `isalnum()`	Character tests
`format(...)`	Format string
`count(sub)`	Count occurrences

Example

s = "  Hello, Python  "
print(s.strip().lower().replace("python", "world"))